1. Field of the Invention
The present invention relates generally to implantable cardiac stimulation devices. More particularly, the present invention relates to an apparatus and method for pacing a heart in its right ventricle or left ventricle as well as pacing the heart in both ventricles.
2. Related Art
Implantable cardiac stimulation devices are well known in the art. Such devices may include, for example, implantable cardiac pacemakers and defibrillators either alone or combined in a common enclosure. The devices are generally implanted in a pectoral region of the chest beneath the skin of a patient within what is known as a subcutaneous pocket. The implantable devices generally function in association with one or more electrode carrying leads which are implanted within the heart. The electrodes are positioned within the heart for making electrical contact with the muscle tissue of their respective heart chamber. Conductors within the leads couple the electrodes to the device to enable the device to deliver the desired electrical therapy.
Traditionally, therapy delivery has been limited to the right portion of the heart. However, new lead structures and methods have been produced and practiced for also delivering cardiac rhythm management therapy from or to the left portion of the heart. For example, it has been demonstrated that electrodes placed in the coronary sinus and great vein may be used for left atrial pacing, left ventricular pacing, cardioversion and defibrillation. These advancements enable implantable cardiac stimulation devices to address the needs of the wide patient population, from those that would benefit from right heart side pacing alone, to those that would benefit from left heart side pacing in conjunction with right heart side pacing (bi-chamber pacing), to those that would benefit from left heart side pacing alone.
For instance, ideally, the left and right ventricle of the heart should contract in the same time frame. A large portion of the population, however, has an enlarged left side of the heart. This enlargement results in failure of the left ventricle to contract with the right ventricle (that is, the contraction of the left ventricle is delayed). Thus, to obtain ventricular synchronization, the left ventricle needs to be stimulated to ensure synchronous contraction of the ventricles.
Therefore, what is needed is an apparatus and method for bi-ventricular pacing of the heart.